The proposed studies will be directed towards elucidating mechanisms of trophic interactions between motor nerves and skeletal muscles; learning more about axonal transport systems in normal and pathological circumstances and studying the mechanism of neuromuscular disorders including myasthenia gravis. In the first part of the project, we will carry out quantitative measurements of acetylcholine receptors of skeletal muscles, after disuse, blockade of cholinergic transmission, and blockade of axonal transport. In the second part, we will study the role of axonal transport in certain experimental neuropathies, and in conditions such as regeneration of nerves. In the third part, we will examine the effects of various aspects of cellular and humoral immune mechanisms in the initiation and maintenance of the myasthenic state in man and animals. BIBLIOGRAPHIC REFERENCES: Drachman, D.B., Fambrough, D.M. (1976) Are muscle fibers denervated in myotonic dystrophy? Arch. Neurol. 33:485-488. Drachman, D.B., Kao, I., Pestronk, A., Toyka, K.V. (1976) Myasthenia gravis as a receptor disorder. Ann. N.Y. Acad. Sci. 274:226-234.